In slaughterhouses, after eviscerating, beheading and chilling, livestock carcasses are, as a first primal cutting step, separated through the spine in two halves of carcass, which are then further processed to obtain other primal cuts. In pork slaughtering, such further primal cuts include hind and front foot, ham, shoulder, loin, back ribs, spare ribs and flank, the latter being further cut to remove spare ribs portion from belly. Heretofore, a common practice used in slaughterhouses for removing ribs from livestock flanks, such as spare ribs in pork flanks, consists in manually removing the ribs portion from the belly of a flank by pulling a hand tool provided with an elongate blade or thread secured at both ends thereof to a pair of handles. Such conventional manual technique has many drawbacks. Manual removing is hazardous and time-consuming for the butchers, and provides relatively poor control on the quality of the end products, which are ribs and beacon being cut from belly. Parameters used as quality criteria generally applied to ribs are average thickness under the ribs, length of the portion tail extending from the first rib, which parameters have to be within respective predetermined ranges, and cut profile which has to generally corresponds to junction of the two main muscles located on the inner side of the flank. As to the separated belly, which should also contain a part of meat, average thickness should be within a predetermined range for optimal classification of belly for bacon production, the range depending on initial flank thickness. The average thickness of meat left under the ribs is one of the most important parameters to control during the cutting operation, which parameter has also great impact on flank classification for bacon. Even for butchers highly skilled in manual rib cutting, a belly may nevertheless be downgraded for bacon due to an insufficient remaining meat thickness thereunder. Therefore, using the foregoing criteria, removed ribs and belly have to be visually inspected and sorted according to predetermined quality grades, which further operations contribute to increase production costs.
In the past years, some butchering systems have been proposed to automate the separation of livestock carcasses in primal cuts, such as the apparatuses disclosed in U.S. Pat. No. 3,159,869 issued on Dec. 8, 1964 to Vogt et al., and in U.S. Pat. No. 4,662,029 issued on May 5, 1987 to Helsene et al. The former patent discloses a semi-automatic apparatus for breaking-up hog carcasses in pieces, including ribs and belly, wherein a light probe connected to an electromechanical controller is manually directed toward a selected one of the carcass portions by an operator to form a light scribe line on the surface thereof, thereby indicating to the controller a target position of a controlled tool as determined by the operator through visual inspection. Such apparatus still requires substantial manual operation. Although the apparatus of Vogt et al. represents an improvement over wholly manual removing technique, it still requires some manual operation. Helsene et al. disclose a prior art automated apparatus for cutting hog carcasses into primal cuts, which apparatus includes a computer vision device, an automated scribe saw to cut the ribs in a vertical plane at a predetermined depth along the back ribs and loin junction, followed by two further parallel automated cutting stations provided to respectively pull the meat part of the loin out from the back ribs and spine and remove spare ribs from belly as part of the flank. The computer vision system includes a camera located above a carrying conveyor for scanning the half carcasses following foot, ham and shoulder removing therefrom, which camera is connected to an image processing computer which locates reference points of the loin and ribs to automatically control the movement of cutting devices used to further separate the half carcass, pull the loin and remove the ribs. The ribs removing station uses a pair of elongate blade support elements projected downwardly from an upper housing secured to a frame and each being connected to one end portion of a V-shaped elongate blade. The housing contains the control elements for vertically adjusting the blade according to the predetermined cutting depth of the scribe saw, and for laterally adjusting one of the blade support relative to the other, according to control information received from the computer. Although the system proposed by Helsene et al. represents an improvement over earlier manual ribs removing technique or prior semi-automatic apparatus, since the computer stores only belly's back fat thickness information, adequate control of the thickness of the remaining meat under the ribs cannot be achieved since the vision system of Helsene et al. does not provide any information about ribs thickness for accurately controlling movement of the cutting blade in a vertical direction.
In U.S. Pat. No. 4,979,269 to Norrie, there is disclosed an apparatus for the separation of back fat from a loin portion of a pork half carcass carried by a lower conveyor under a pressure device, which apparatus uses a generally arcuate blade interposed between the conveyor and the pressure device and being movable relative to the conveyor according to thickness as measured between the visible back fat and meat portions of the loin portion at an edge thereof, using a flank edge facing camera as part of an optical sensing device. However, such measurement principle cannot be adequately applied for ribs removal since back fat thickness being not even throughout the back surface of the flank, remaining meat thickness under ribs cannot be derived from a measurement of the back fat thickness at a visible edge of the flank.
In PCT published application 91/04670 to Khodabandehloo, there is disclosed a robotized cutting apparatus for separating meat from bones, which apparatus comprises a robot having a robot arm provided with a cutting tool having a cutting blade and having a force sensor at a free end thereof, and a processing unit including a force feedback device receiving sensed force signals and having an output connected to a robot controller. Cameras are connected to a vision processing unit having a first output being coupled to a decision processing unit, and second output being coupled to a data update processor feeding a memory for storing information about previous carcasses, the decision processing unit having access to the stored data. The cameras are used with the vision processing unit to determine the spatial coordinates of a number of position on the carcass, for example the positions of a particular bone. The stored data include the coordinates of the particular positions of the carcasses, and of the cutting paths that were followed by the cutting blade to remove meat from the carcasses. If the new data correspond closely to the data relating to an earlier carcass, this relationship is used to determined the starting point of the cutting path for the new carcass. If such relationship cannot be found, a new cutting path entry point is derived. Then, the cutting blade is moved through the carcass meat according to an initial direction and angular position until the sensed reacting force acting thereon raises beyond a predetermined threshold level corresponding to a hard material such as bone, and the movement and angular position is corrected accordingly in a feedback mode of operation. The current position coordinates of the cutting blade is continuously compared to stored cutting path data corresponding to a selected previous comparable carcass, to provide further correction if required. However, since reaction force monitoring technique used by the apparatus aims at avoiding meat left under the bones, such prior art apparatus cannot be useful for ribs removing, control of the meat thickness left under ribs being an important quality requirement.